Extraction of trivalent americium and europium from nitric acid solution with a calixarene-based diglycolamide

• A new calixarene derivative with diglycolamide units (calix[4]arene-BDGA) was synthesized for treatment of HLLW.
• The extraction behaviors of calix[4]arene-BDGA for Am(III) and Eu(III) in nitric acid solution were investigated in detail.
• Calix[4]arene-BDGA has not only high distribution ratio, but also good separation factor for Eu(III) and Am(III).
• Solvent extraction thermodynamics parameters were presented for the first time.

A ligand derived from calix[4]arene functionalized at the lower rim with four diglycolamide (DGA) binding units containing n-butyl groups, which is denoted as calix[4]arene-BDGA, was synthesized and characterized by MS, 1H NMR and 13C NMR. The extraction behaviors of Am(III) and Eu(III) from nitric acid solution were investigated with calix[4]arene-BDGA in 95% kerosene/5% n-octanol (v/v). Effects of acidity, concentration of extractant and temperature on the distribution ratio of Am(III) and Eu(III) were evaluated. The results indicated the distribution ratio values of Am(III) and Eu(III) increase with the increase of nitric acid concentration in the examination of acidity range from 0.5 to 5.0 mol/L. The ligand has a higher selectivity for Eu(III) than for Am(III) with the separation factor SFEu(III)/Am(III) values of 4.5–7.3. Slope analysis from nitric acid medium indicated that Am(III) and Eu(III) were extracted as di-solvated species by calix[4]arene-BDGA. The extraction mechanism was described and the thermodynamic parameters (ΔH, ΔS and ΔG) were also presented.